340 SUPERIOR VENA CAVA. 



It is in relation in front with the left 

 Fig. 121.* sterno-clavicular articulation and the 



first piece of the sternum. At its com- 

 mencement it receives the thoracic 

 duct which opens into it from behind, 

 and in its course is joined by the left 

 vertebral, left inferior thyroid, left mam- 

 mary, and by the superior intercostal 

 vein. It also receives some small veins 

 from the mediastinum and thymus gland. 

 There are no valves in the venae innomi- 

 nate. 



SUPERIOR VENA CAVA. 



The superior cava is a short trunk 

 about three inches in length, formed by 

 the junction of the two venas innominatae. 

 It descends perpendicularly on the right 

 side of the mediastinum, and entering the 

 pericardium terminates in the upper part 

 of the right auricle. 



It is in relation in front with the tho- 

 racic fascia, which separates it from the 

 thymus gland, and with the pericardium; 

 behind with the right pulmonary artery, 

 and the right superior pulmonary vein; 

 internally with the ascending aorta ; ex- 

 ternally with the right phrenic nerve, and 

 right lung. Immediately before entering 

 the pericardium it receives the vena 

 azygos major. 



INFERIOR VENA CAVA, WITH ITS FORMATIVE BRANCHES. 



Iliac Veins. 



The External iliac vein lies to the inner side of the corresponding 

 artery at the os pubis ; but gradually gets behind it as it passes 



* The veins of the trunk and neck. 1. The superior vena cava. 2. The left vena 

 innominata. 3. The right vena innominata. 4. The right subclavian vein. 5. The 

 internal jugular vein. 6. The external jugular. 7. The anterior jugular. 8. The 

 inferior vena cava. 9. The external iliac vein. 10. The internal iliac vein. 11. The 

 common iliac veins; the small vein between these is the vena sacra media. 12, 12. 

 Lumbar veins. 13. The right spermatic vein. 14. The left spermatic, opening into 

 the left renal vein. 15. The right renal vein. 16. The trunk of the hepatic veins. 

 17. The greater vena azygos, cornmeneing inferiorly in the lumbar veins. 18. The 

 lesser vena azygos, also commencing in the lumbar veins. 19. A branch of communi- 

 cation with the left renal vein. 20. The termination of the lesser in the greater vena 

 azygos. 21. The superior intercostal vein; communicating inferiorly with the lesser 

 vena azygos, and terminating superiorly in the left vena innominata. 



